Screen



1943- w. c. JOHNSON 2,334,707

SCREEN Filed Jan. 26, 1942 Patented Nov. 23, 1943 SCREEN William C. Johnson, Wauwatosa, Wis., assignor to Allis-Chalmers Manufacturing Company, Milwaukee, Wis., a corporation of Delaware Application January 26, 1942, Serial No. 428,191

4 Claims.

This invention relates to screens and was developed primarily to meet the exacting requirements cloth sections are supported by transverse supporting members; and in which at least certain of said transverse members are longitudinally adjustable to tension said screen cloth longitudinally of said screen.

In the drawing illustrating specific embodiments of this invention:

Fig. 1 is a central longitudinal sectional view of a vibrating screen provided with screen cloth sections in accordance with this invention;

Fig. 2 is a fragmental sectional view similar to Fig. l, but on an enlarged scale;

Fig. 3 is a section taken on line III of Fig. 1;

Fig. i is a transverse sectional view of a modified screen structure;

Fig. 5 is a fragmental sectional view illustrating a modified and intermediate transverse supporting member; and

Fig. 6 is an enlarged fragmental sectional view of standard woven screen cloth, indicating the effect of abrasive wear on the screen cloth.

While a specific type of vibrating screen is disclosed, the invention is equally applicable to any other known type of fixed or vibrated screen. 7 As used in the specification and claims, screen deck refers to the frame which carries the screen cloth; while "screen cloth refers to either woven screen or perforated metal screen.

One of the major expenses in the screening of ores, stone, sand and other abrasive materials is the cost of screen cloth replacement. The wear on the screen cloth is especially severe when the standard woven screen cloth is utilized, since in such cases the projecting portions are rapidly worn off, necessitating the discard of screen cloth which is only partially worn.

Fig. 6 illustrates such wear. In Fig. 6, the threads running in one direction are illustrated at III, while the cross-threads are indicated at H. The upper surfaces of the upwardly protruding portions of threads II are indicated at l2. These protruding portions of threads II are subject to excessive wear. After these protruding portions are worn down to the condition indicated by dotted lines l3, there is very little life left in the screen cloth, as the threads will soon begin to break. If, before this degree of wear has been reached, the screen cloth is reversed to expose the unworn bottom surface to the material being screened, the life of the screen cloth can be nearly doubled.

A further-advantage of reversing the screen cloth longitudinally (rather than transversely of the path of flow of material being screened) results from the fact that in substantially all cases the wear on any section of screen cloth is greater at the feed end than at the discharge end. By reversing a screen cloth section longitudinally (or end for end), the former discharge end becomes the feed end, thereby equalizing the wear over the length of the screen, and resulting in longer wear of the screen cloth. Such saving in material is of particular importance at a time when cloth materials and finished screen cloths are diflicult to procure.

The screen illustrated in Fig. 1 comprises a deck having side walls l5 and suitable transverse connecting members I6 and IT. The deck may be suitably supported by means of cables l8 and is vibrated by rotation of main shaft IS. The specific vibrating mechanism is not illustrated, since it is not material to the invention. Side plates l5 may carry longitudinal angle irons 2| rigidly attached to side plates I5 by riveting or otherwise. The screen deck also carries a plurality-of transverse tubular or other members 22 which may be covered with protective rubber jackets 23. It will be noted that angle irons 2| and tubular members 22 are arranged in somewhat arcuate form rather than in a straight line, so that the screen cloth supported thereon is longitudinally crowned at the middle. The screen deck is also provided with an intermediate transverse supporting member 24 which may be rigidly connected to side plates l5. I

The screen deck carries a plurality of screen cloth sections 26 and 21. As illustrated, each of these screen cloth sections is provided with an upwardly directed end hook 28 at the feed end and a downwardly directed end hook 28' at the at all times.

Helical springs 32 may be utilized to Screen cloth section 2115 similarly retained by intermediate transverse member 24 at one end and an adjustable retaining hook or plate 26' at the other end.

Each screen cloth section is supported at its intermediate portion by means of rubber covered members 22, the side edges of the screen cloth being supported by angle irons 2|. Obviously any desired number of screen decks may be utilized, and the screen may be vibrated by means of any known vibrating mechanism.

While Figs. 1 and 2 illustrate a Z-shaped intermediate transverse member 24, it is obvious that any other cross-sectional form of intermediate transverse member may be utilized, so long as it provides oppositely extending projections or other hook strip engaging means to engage screen cloth end hooks. For example, Fig. illustrates an intermediate transverse supporting member 34 which serves the same function as member 24 in Fig. 2.

While longitudinal reversal of screen cloth sections is preferred because it permits the area of maximum wear to be distributed over the length of the screen section, the invention is not limited to such longitudinal reversal of screen cloth sections. Fig. 4 illustrates a construction in which transverse reversal of screen cloth sections is provided. In this figure, screen deck side walls I5 I are provided with adjustable screen engaging tension plates 36, 36", which engage screen cloth section 31, which is provided with longitudinal end hooks 38 and 38, end hook '36 being directed upward while end hook 38 is directed downward. In this modification, screen cloth section 31 may be turned over transversely. so that both sides of the screen cloth may be utilized.

In the operation 01- the screen illustrated in Figs. 1 and 2, screen cloth sections 26 and 21 are mounted as shown, and necessary tension is applied by means of screws 30 and nuts 3|. The screen may then be utilized for screening material. During operation of the vibrating screen,

material is fed onto the screen at the left of.

Figs. 1 and 2 and proceeds along screen section 26 while it is being screened. Due to the crowning of screen cloth section 26, some desired variation in the speed of the material traveling along the screen is obtained, and the customary decrease in speed at the discharge end of each section is eliminated. Upon reaching the discharge end of section 26, material is discharged onto screen section 21, the fall from screen section 26 to section 21 resulting in elimination of any stratification which may have occurred, so that amore eflicient screening action is secured on screen section 21. The screening action is then continued on section 21 until the material is discharged from the screen.

Screen sections 26 and 2'! are preferably constructed so that they will have the same length, so that these two screen sections may be easily interchangeable. Screen section 26, being at the feed end of the screen, is subjected to greater wear than screen section 21. In case spare sections are not available, it may be desirable to exchange the positions of screen sections 26 and 21 in order to extend the duration of operation of the screen before new sections must be obtained. Moreover, each of the two screen sections is easily reversible by loosening of nuts 3! on screws 30 and simple longitudinal turning over of each screen cloth section. This reversal of screen sections results in greatly increased wear before the screen section must be discarded. The screen sections of the various decks are of the same dimensions, so that screen sections may be interclganged between various decks, if that is desira le.

The invention is clearly susceptible of variations and modifications within the range of those skilled in the art, and is limited only by the scope of the claims appended hereto.

It is claimed and desired to secure by Letters Patent:

1. A vibrating screen comprising a vibrated deck having longitudinal side members, transverse members connecting said side members, and

a plurality of separate sections of screen cloth arranged longitudinally along said deck, each of said sections being providedwith identical rigid hook strips at the feed end and discharge end of each section, each of said hook strips having a recurved portion directed in the same direction of rotation with respect to the intermediate portion of said sections, and edge means on said transverse members for freely entering said recurved portions of said hook strips in hooked relation so constructed and arranged that each of said sections is reversibly attachable to said deck.

2. A vibrating screen as defined in claim 1, wherein said screen sections are substantially equal in length, whereby said sections are both interchangeable and reversible.

3. A screen deck comprising a screen frame having a feed end and a discharge end, a transverse hook member arranged at each of said ends, means for adjusting said transverse members longitudinally of said deck, an intermediate transverse member carried by said deck, two

screen cloth sections having hook strips at their ends, the hook strips of one screen cloth section removably engaging said feed end transverse member and said intermediate transverse member, and the hook strips of the other of said screen cloth sections removably engaging said intermediate transverse member and said discharge end transverse member, said hook strips of each screen cloth section extending in the same rotary direction about an intermediate portion of said hook strip.

4. A screen deck as defined in claim 3, said intermediate transverse member being Z-shaped in a section taken longitudinally of said screen deck, whereby the adjacent end hooks of said screen cloth sections engage the free edges of said Z-shaped member.

WILLIAM C. JOHNSON. 

